Flow control of pulverant material



Dec. l, 1964 E. J. osrRowsKl E'rAL. 3,159,432

- FLOW CONTROL OF PULVERNT MATERIAL Filed May 22, 1962 2 Sheets-Sheet 2 v BY HAROLD A. PUTNAM `6 ATTORNEYS.

United States Patent() 3,159,432 FLOW CNTRL @E PULVERANT MA'EEAL Edward l. Gstrowski, Steubenville, hio, and Hiram C Kozak, Lackawanna, and Harold A. Putnam, Buffalo, NSY., assignors to National Steel Corporation, a corporation of Delaware Filed May 22, 1962, Ser. No. 196,767 Ll Claims. (Cl. 392-53) This invention relates generally to controlling flow of finely divided solids and, more particularly, to improved methods and apparatus for uniformly feeding pulverant material into a flowing gas stream at a. constant rate.

In the past, schemes for feeding finely divided solids have generally relied von gravity and/ or mechanical vibration, magnetic properties of the material or'mechanical feed rotors. Percise control of pulverant material ow has however been lacking in the art. The pneumatically controlled system disclosed herein provides precise control of pulverant material flow while meeting such requirements as continuous operability, uniform and constant flow rate, and feed into a variable pressure system.

A difficult problem in pulverant material distribution is obtaining and maintaining fluid flow properties in the finely divided material being distributed. This problem is compounded in a pressure controlled system since steps reference Will'be had tothe accompanying drawings whereinlike numbers are used to ldesignate like structures. In these drawings,

FIGURE l is a schematic diagram apparatus for introducing pulverant material into a blast furnace system, and

FIGURE 2 is a detailed schematic diagram of portions of FIGURE 1 including control apparatus for iutroducing a pulverant material into a system.

Referring to FIGURE 1, pulverant material from source 9 is supplied via conveyance means lo and 11 to storage tanks 14 and 15, respectively. Conduit 16 connects storage tank i4 in series with injector tank 18; storage tank l5' is similarly connected through conduit 17 with injector tank 19. Pulverant material is delivered from injector tanks 13 and i9 through identical distributor conduits Z2. Carrier gas pipes 23 areV in receiving relationship to distributor conduits Z2 and deliver the pulverant material to the tuyeres of blast furnace 2d. Hot blast j is delivered to the blast furnace 25 Via bustle pipe 2S and to maintain fluid flow properties in the pulverant material are likely to upset the pneumatic control. In overcoming this and other problems, the teachings of the invention make possible a pneumatic system for pulverant material distribution which functions with accuracy comparable to that available in gaseous or liquid flow control systems. ln so doing, pulverant materialsmay be used in applications where heretofore, their use has been practically nonexistent. As an example of the latter, liquid and gaseous fuels have been used increasingly in the steel industry to supplant coke in blast furnaces. Pulverized solid fuels have not been able to meet operational requirements and have not been used commercially. With the teachings of the present invention, however, flow control pulverant material is available permitting pulverized solid fuels to be used equally as well as liquid or gaseous fuels .in supplanting blast furnace coke. As a result, the more costly coke can be replaced by a less costly fuel coal.

Flou/,control requirements in iron producing operations are as arduous'as can be found in most commercial opera-V tions, therefore the invention will be described in this environment. ln the blast furnace art, a portion of the blast furnace coke which is normally introduced at the top of Ithe furnace can be replaced with an auxiliary fuel are utilized. When supplanting a portion of this coke nace, .these auxiliary fuels must be introduced uniformly with auxiliary fuels `introduced at the bottom of the furi i so over extended periods of time to provide the quantitative Yblast (l) on a continuouslyk available basis, V(2)'` over unlimited periods of time and (3) with uniformity independent of variations in blast lpressure.` In describing a specific embodiment of the invention hot blast main 26. v

Pneumatic pressure for the pulverant material distribution system is supplied from gas source 27. Conduits 23 and 29 supply carrier gas to pipes 23. Conduits 3d and 3l. supply gas from gas source 27 :to pulverant ow control means 32 and 33, respectively. The pneumatic pressure supplied through pulverant Vmateiral iiow control means 32 and 33 to the injector tanks and i9, respectively, controls the amount of pulverant material delivered to the blast furnace system. More specifically, the amount of pulverant material distributed is dependent upon the difference in pneumatic pressure between the higher-pressure injector tanks and the lowerpressure delivery point in the blast furnace system. However, pressure -diflerential alone is not sufiicient to maintain flow of pulverant material. Without the additional structures and control features provided, to be described, pulveran-t material would merely pack about the area of distributors 22 and it would be impossible to obtain flow when desired.

In FIGURE 2, a portion of `the distribution system of FIGURE 1 is shown with such additional structure and control features in more detail. The injection system is rendered continuously operable by connection of the storage tanks and injector tanks in series. With this arrangement, an injector tank may be recharged from a storage tank with both tanks on the line and a storage injector tank may be isolated from the injector tank for recharging while the series connected injector tank remains on the line. Valve 3o opens or closes conduit lo.

and includes vent valve d; vent line Sti is connected to storage tank lo and includes valve 52; vent lines lo and Ell are interconnected by crossover line E4 which includes va valve- 5o, and pressurizing conduit o@ is connected to injector tank l and includes i'iow control valve 62.

Apressure differential between injector tank 1S and the blast furnace system is in itself not suiicient to cause uniform Bow because of packing of pulverant materialV at the bottom of injector tank l. To offset this difhculty a iuidizing cone 6ft is provided at each distributor tube v.7l-2.. Fluidizing gas continuously discharges tangentially within cones 4to maintain the pulverant material in a fluid or semi-fluid state and responsiveto pressure con-1 Vent valves 4S and 52 normally vent to the atmosphere. However, after refilling of storage tank 14, this tank may be brought up to a pressure approximating that of injector tank 1S by venting injector tank 18 into storage tank 14. In this operation, vent valves 4S and 52 and auxiliary pneumatic pressure valve 70 are closed. Crossover valve 56 is opened and injector tank i8 is ente-d into storage tank le. When the pressure in storage tank 14 equals that in injector tank lll, valve 56 may be closed and vent valve de opened to vent injector tank 13 to the atmosphere or venting may be controlled through valve S2, and storage tank t4 maintained it the same pressure as injector tank i8 via crossovenl-i. iliese operations can be made automatic by solenoid operated valves or pressure sensitive valves.

With the .apparatus thus `far described, the injector tank 1 pressure rises or falls with lthe hot blast main 26 pressure. ln the event the hot blast main pressure falls radially, for example during casting of the blast furnace, it is not desirable to have the injector tank pressure follow down the full scale because of a time lag which can be incurred when bringing the injector tank 18 pressure up to the required level Kafter hot blast main pressure is restored. To overcome this problem, provision is made to automatically stop venting when the hot blast main pressure falls below a selected point. To execute this control feature, the blast main pressure measurement'is delivered over signal line $8 to pressure switch 160 in circuit 10?.. Closing of switch lli@ delivers powerto relay ltld which opens switch ltlta terminating delivery of power to vent valve interlock 9d. This sto-ps venting or the injection system until the pressure in the liot blast main 2d returns to the selected level; at this point, normal venting control takes over. v

ln utilizing this invention for injecting pulverized fuel into a blast furnace system the percentage of blast furnace coke to be replaced is determined and the flow rate of pulverized fuel required is calculated. Plmong other things, the type of pulverizedfuel affects this 1cai-.- culation; typical fuels inclu-de pulverized coal, coke, criar, or other earbonaceous materials. The gas employed may also atleet this calculation; normally air would be employed, but enrichment with oxygen or gaseous fuels is also within the scope of the invention. It may also be desirable to add other lpulverized materials such as lime, ores, blast furnace lines, etc., `and provision can be made for adding these materials in addition to or in place of the pulverized fuel. Considering addition or pulverized fuel only, after determining the desired percentage of total fuel requirement to be injected as auxiliary fuel (typically upto about 30%), the required flow rate, in weight units per unit of time is calculated. The required pressure differential to maintain this flow rate is predetermined and introduced to differential pressure control l5 las previously pointed out. Injector tank i3 is brought up to original pressure via iiow control valve 62 and iow of pulverized fuel is initiated. Flow is then maintained under the controls described. injector tank ld is periodically recharged from storage tank le utilizing the cycle of operation described earlier. The sequential operaion of pressurizing,y venting, and recharging valves can be timed |and operated automatically by sequence timer,

Mitt within the teachings of the invention. Operation of a sequence timer is well known in the art and, with the cyclical operation described herein, no further explanation for automatic operation should be required by one skilled inthe art. r

The methods and apparatus describe-d herein may be utilized for pressured-.controlled introduction of iinely divided solids into a `pressurized or non-pressurized system `and can maintain uniform dow at a constant flow rate `of the material on. a continuously operable basis.

l. Apparatus AVfor pneumatioally providing a kuniform and constant flow rate of pulverant material into a variable pressure blast furnace system comprising injector tank means for holding pulverant material under pressure, pneumatic pressurizing means for maintaining the injector tank means under pressure including pneuf matic flow control valve means, distributor means for delivering pulverant material from the injector tank means including uiidizing means for the pulverant material contiguous with the distributor means, conduit means for delivering fluidizing gas to the fluidizing means to continuously maintain pulverant material in a tiuid state, venting means for the injector tank means including vent control valve means, control means for maintaining a substantially constant pressure differential between the injector tank means and the blastvfurnace system while maintaining pulverant material in a iluidized state, the control means including, means for measuring the pressure differential between the injector tank means and the blast furnace; system pressures, means for comparing the measured pressure differential to a predetermined desired pressure differential and generating a signal in response thereto to control the ilow control valve means and the vent control valve means to maintain a constant pressure dilferential between the injector tank means and the blast furnace system. 2. Apparatus for pneumatically-providing a uniform and constant flow rate of pulverant material into a variable pressure blast furnace system on a continuously operable basis comp-rising storage tank means for storing pulverant material under pressure,

injector tank means for holding pulverant material under pressure,

conduit means interconnecting the storage tank means and injector tank means for recharging-the injector tank means from the storage tank means while mairitaiin'ng the storage and injector tank means under pressure,

pneumatic pressurizing means for maintaining the injector tank means under pressure including pneumatic iiow control means for raising pneumatic presssure within `the injector tank means to selective levels,

distributor means for delivering pulverant material from the injector tank means including fluidizing means contiguous with the distributor means,

means for deliveringV fluidizing gas to the iluidizing lmeans to continuously maintain pulverant material about to be delivered from the injector tank means in a fluid state,

venting means for the injector ltank means and the storage tank, means including vent control means,

pressure equalizing means connected between the injector tank means and the storage tank means, and

control means for maintaining a substantially constant pressure differential between the injector tank means' and the blast furnace system including v means for measuring the pressure differential between the injector tank means and the blast furnace system, vmeans for comparing the measured pressure differential to a predetermined pressure differential and generating a signal for controlling the flow control valve means and the vent control valve means, and means for terminating venting of the injector tank means when pressure of the blast furnace system falls below a pre-selected level. v 3. Method for injecting pulverant solid fuel into an iron producing blast furnace system at a uniform rate in which pulverized solid fuel held in container means under pressure is continuously available to be delivered to the blast furnace system for entrailment in the hot blast main comprising the steps of supplying gas to the container means for the pulverized solid fuel to maintain the container means under pressure, continuously supplying fluidrized gas to the container means for maintaining pulverized solid fuel about to be delivered from the container means in a fluid state, measuring the pneumatic pressure of the container means, measuring the pneumatic pressure at a pre-selected reference point in the hot blast main, measuring the pneumatic pressure differential between the pneumatic pressure of the container means and the hot blast system, and controlling supply of pneumatic pressure to the container means and venting of the container means to maintain a predetermined pneumatic pressure differential. 4. Apparatus for pneumatically providing a uniform and constant ow rate of pulverant material into a pressurized gas stream on a continuously operable basis comprisins .a storage tank means for storing pulver-ant material under pressure, injector tank means for holding pulverant material under pressure,

conduit means interconnecting the storage tank means and injector tank means for recharging the injector tank means from the storage tank means while maintaining the storage and injector tank means under pressure,

pneumatic pressurizing means for maintaining the injector tank means under pressure including pneumatic ilow control means for raising pneumatic pressure within the injector tank means to selective levels,

distributor means for delivering pulverant material from the injector tank means including luidizing means contiguous with the distributor means,

means for delivering iluidizing gas to the uidizing means to continuously maintain pulverant material about to be delivered from the injector tank means in -a fluid state,

venting means for the injector tank means and the storage tank means including vent control means,

pressure equalizing means connected between the injeetor tank means and the storage tank means, and

control means for maintaining a substantially constant pressure differential between the injector tank means and the pressurized gas stream including means for measuring the pressure differential between the injector tank means and the pressurized gas stream,

means for comparing the measured pressure differential to a predetermined pressure differential and generating a signal for controlling the flow control valve means and the vent control valve means, and

means for terminating venting of the injector tank means when pressure of the pressurized gas stream falls below a preselected level.

References Cited in the tile of this patent UNITED STATES PATENTS 1,943,589 Domina Jan. 16, 1934 2,684,870 Berg July 27, 1954 2,707,132 Baresch Apr. 26, 1955 

1. APPARATUS FOR PNEUMATICALLY PROVIDING A UNIFORM AND CONSTANT FLOW OF PULVERANT MATERIAL INTO A VARIABLE PRESSURE BLAST FURNACE SYSTEM COMPRISING INJECTOR TANK MEANS FOR HOLDING PULVERANT MATERIAL UNDER PRESSURE, PNEUMATIC PRESSURIZING MEANS FOR MAINTAINING THE INJECTOR TANK MEANS UNDER PRESSURE INCLUDING PNEUMATIC FLOW CONTROL VALVE MEANS, DISTRIBUTOR MEANS FOR DELIVERING PULVERANT MATERIAL FROM THE INJECTOR TANK MEANS INCLUDIONG FLUIDIZING MEANS FOR THE PULVERANT MATERIAL CONTIGUOUS WITH THE DISTRIBUTOR MEANS, CONDUIT MEANS FOR DELIVERING FLUIDIZING GAS TO THE FLUIDIZING MEANS TO CONTINUOUSLY MAINTAIN PULVERANT MATERIAL IN A FLUID STATE, VENTING MEANS FOR THE INJECTOR TANK MEANS INCLUDING VENT CONTROL VALVE MEANS, CONTROL MEANS FOR MAINTAINING A SUBSTANTIALLY CONSTANT PRESSURE DIFFERENT BETWEEN THE INJECTOR TANK MEANS AND THE BLAST FURNACE SYSTEM WHILE MAINTAINING PULVERANT MATERIAL IN A FLUIDIZED STATE, THE CONTROL MEANS INCLUDING, MEANS FOR MEASURING THE PRESSURE DIFFERENTIAL BETWEEN THE INJECTOR TANK MEANS AND THE BLAST FURNACE SYSTEM PRESSURES, MEANS FOR COMPARING THE MEASURED PRESSURE DIFFERENTIAL TO A PREDETERMINED DESIRED PRESSURE DIFFERENTIAL AND GENERATING A SIGNAL IN RESPONSE THERTO TO CONTROL THE FLOR CONTROL VALVE MEANS AND THE VENT CONTROL VALVE MEANS TO MAINTAIN A CONSTANT PRESSURE DIFFERENTIAL BETWEEN THE INJECTOR TANK MEANS AND THE BLAST FURNACE SYSTEM. 